OBJECTIVES: Among individuals living with schizophrenia or bipolar disorder, several reasons for non-adherence to antipsychotic medication have been cited, including attitudes about medication and side-effects. It has been shown that medication non-adherence is associated with increased utilization of healthcare resources.

METHODS: We used electronic health records (EHR) data to identify individuals with at least one 60-day period of suspected continuous use of antipsychotics between 2005 and 2019. Adult patients were identified with bipolar and schizophrenia spectrum disorders, or psychiatric controls (neither a schizophrenia nor bipolar diagnosis). We examined the association of acute care utilization (all cause ED visits and inpatient admissions) with medication adherence and medication switching during the first 180 days of treatment. Adherence was defined as proportion of days counts (PDC) greater than 0.8. The antipsychotic medication exposure variable was a combination of adherence and switching to account for an interaction between the two measures.

RESULTS: After adjusting for prior utilization and medical comorbidity, patients who were non-adherent without switching medications were more likely to have an inpatient admission (OR=1.58, 95% CI=[1.20, 2.08]) than patients who were adherent to their first antipsychotic medication. Patient who switched antipsychotic medications were more likely to have an inpatient admission than patients adherent to initial antipsychotic medication (switched and adherent (OR=2.77, 95% CI=[1.82, 4.21]); switched and non-adherent (OR=2.24, 95% CI=[1.48, 3.39])). Finally, patients who completely stopped antipsychotic medication were more likely (OR=1.77, 95% CI=[1.29, 2.41]) to have an inpatient admission during the first 180 days of treatment compared to patients who were adherent to their first antipsychotic medication. We obtained similar results when examining the effect of non-adherence and medication switches on any ED visit and the number of ED visits.

CONCLUSIONS: Non-adherence and medication switches were both associated with increased acute care utilization during the first 180 days of treatment.